1969 Merc 500 slow cranking speed, wont turn over

[WinnipegJet91]

I just acquired a 1969 Merc 500 that was on my 1964 Starcraft Jet. The motor is having a very hard time turning over and never actually does start. The starter and solenoid are either been replaced by the PO or original. When the starter engages the flywheel it might get a 1/4 turn then stop. I'm using a fully charged battery (750 cca) I can pull all the plugs and the starter will spin the engine with no problem at all so the motor isn't seizing up or sticking. When I have all the plugs in, and only take one out at a time it doesn't help the cause.

I took the starter motor out (third time) and took it apart, cleaned off the contacts and put it all back together. With no luck at starting it kept turning the flywheel only 1/4-1/2 way, on the second try a spark came from the negative terminal on the battery and the motor will no longer turn over, may have fried the solenoid. I will be replacing the solenoid this weekend from my parts motor but I don't have high hopes.

What should I look for next? Might the exhaust port be plugged?

Any advice would be a great help!

 

[GA_Boater]

The spark was caused by loose or poor contact on the battery. Clean both posts and the connectors.

 

[WinnipegJet91]

The spark was caused by loose or poor contact on the battery. Clean both posts and the connectors.

I installed the new solinoid and all is good, other than it still doesn't start.

I have also skipped the battery completely and connected straight to the starter motor and the same issue happens.. Still unsure what the next step is.

I've ordered a new starter to hopefully fix the starting problem.

 

[flyingscott]

Does the flywheel turn easy by hand or does it feel like it was binding.

 

[WinnipegJet91]

Does the flywheel turn easy by hand or does it feel like it was binding.

By hand you can turn the flywheel about a quarter turn.. tried with a pull cord and same deal, very tough that's for sure. tougher than i was expecting.. but when i pull a couple spark plugs out.. it turns with grace provided it's allowing some combustion to escape through the spark plug holes..

 

[flyingscott]

Take the lower unit off and see if the motor turns easier

 

[WinnipegJet91]

Take the lower unit off and see if the motor turns easier

Sounds like a good idea, I will give that a try. I dumped a whole can of Seafoam into the cylinders/Carbs/fuel tank and we got some momentum. It starts but right away dies out.. good thing is I was able fog for mosquitoes.. lots of blueish exhaust came out in the 3 seconds it ran before quiting on me. (typical for a two stroke I think)

When it did run for those 3 seconds, there's a lot of loud metal on metal noises almost like a clunking sound in the lower end. I made sure the gear oil was also topped off before attempting this. When I eventually turned the water off, a lot of gear oil (I think) or left over unburned fuel leaked out of the lower end onto my makeshift water ramp (garage is sloped the wrong way).

As I've mentioned before, any tips or procedures to help me get this thing going is greatly appreciated. Definitely new to the outboard scene as I've ran inboards only in the past.

unfortunately i do not have a video of the motor starting.. was too excited that i heard some pop! ha

 

[racerone]

Check the flex plate on the flywheel.---A thin round metal plate on top.---Might be cracked.----Remove bypass covers and inspect pistons / rings and movement of those pistons.

 

[444]

Put a ratchet on the crankshaft nut at the flywheel. You should be able to turn it over by hand with some (but not a ton) effort. If no-go and you're sure it's in neutral, drop the lower unit. I had a bad one lock the engine solid. If now reasonable to turn over by hand but the starter won't do it, suspect the brushes in your starter. The are cheap and easy to change. Next could be windings in the starter. If you have a spare starter you can try, do.